Yarn detector switch-lower

ABSTRACT

A yarn detector switch for monitoring the yarn before it enters the knitting machine to stop the knitting machine and light an indicator lamp under abnormal conditions that it detects such as a broken yarn or yarn runs out. This yarn detecting switch stops the machine quickly to prevent the yarn end from being drawn into the machine needles which if allowed to occur would cause a fabric defect entailing considerable cost in time and money. In this yarn detector switch, parts that wear have been made readily replaceable, a unitary tension guide has been provided with snapin mounting onto the switch housing making it readily removable, all the ceramic eyelets are readily removable, and a trapper has been provided for trapping the yarn to prevent machine shutdown under normal slackening of the yarn when knitting certain patterns.

United States Patent [191 Hopkins Nov. 19, 1974 1 YARN DETECTOR SWITCH-LOWER [75] Inventor: Alton W. Hopkins, Newtown Square, Pa.

[52] US. Cl 66/163, 28/51, 57/81,

ZOO/61.13, ZOO/61.18 [51] Int. Cl D04b 35/14 [58] Field of Search 66/163, 157, 161; 28/51,

28/7l.4; 57/81; ZOO/61.13, 61.14, 61.18; 340/259; 307/119 3,772,487 11/1973 Levin ZOO/61.13

FOREIGN PATENTS OR APPLICATIONS 811,704 4/1959 Great Britain 66/163 Primary Examiner-James Kee Chi Attorney, Agent, or Firm-H. R. Rather; Wm. A. Autio [5 7] ABSTRACT A yarn detector switch for monitoring the yarn before it enters the knitting machine to stop the knitting machine and light an indicator lamp under abnormal conditions that it detects such as a broken yarn or yarn runs out. This yarn detecting switch stops the machine quickly to prevent the yarn end from being drawn into the machine needles which if allowed to occur would cause a fabric defect entailing considerable cost in time and money. In this yarn detector switch, parts that wear have been made readily replaceable, a unitary tension guide has been provided with snap-in mounting onto the switch housing making it readily removable, all the ceramic eyelets are readily removable, and a trapper has been provided for trapping the yarn to prevent machine shutdown under normal slackening of the yarn when knitting certain patterns.

9 Claims, 6 Drawing Figures PATENTEL HOV I 9 I874 SHEET 10F 2 PAH-INTEL UV 1 9 I974 SHEEI 2 OF 2 .IIIEIJE. F.

YARN DETECTOR SWITCH-LOWER BACKGROUND OF THE INVENTION Yarn detector switches and yarn break detecting devices have been known heretofore such as those shown in .I. Wachsman U.S. Pat. No. 2,599,595, June 10, 1952; E. Vossen US. Pat. No. 3,094,855, June 25, 1963; and British Pat. No. 811,704, published Apr. 8, 1959.

While these prior devices have been useful for their intended purposes, this invention relates to improvements thereover.

SUMMARY OF THE INVENTION This invention relates to yarn detector switches for use where the yarn enters the knitting machine for detecting the yarn and stopping the machine when a break in the yarn or end of yarn condition occurs.

An object of the invention is to provide an improved yarn detector switch.

A more specific object of the invention is to provide a yarn detector switch or yarn break detector with improved, readily replaceable wear parts.

Another specific object of the invention is to provide a yarn detector switch with an improved unitary tension guide having snap-in mounting to the switch housing affording ready removal.

Another specific object of the invention is to provide a yarn detector switch with readily removable ceramic eyelets.

Another specific object of the invention is to provide a switch or yarn detector with a readily removable trapper for trapping the yarn and thereby preventing machine shutdown under normal slackening of the yarn when knitting certain patterns.

Other objects and advantages of the invention will hereinafter appear.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged exploded isometric view of a yarn detector switch constructed in accordance with the invention;

FIG. 2 is a front elevational view thereof with the front cover removed to show the internal parts;

FIG. 3 is a left side view thereof;

FIG. 4 is a vertical cross-sectional view taken along line 4-4 of FIG. 2;

FIG. 5 is an isometric view of the stationary contact plate thereof shown in FIG. 2; and

FIG. 6 is a schematic circuit diagram thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. l-3, there is shown a yarn detector switch according to the invention. This lower switch is positioned near the point where the yarn enters the knitting machine in order to be able to stop the machine before the end of the yarn enters the knitting needles. While a single yarn detector switch has been shown, it will be apparent that a plurality of like yarn detector switches are adapted to be mounted side-byside along a supporting and electrically conducting rail for monitoring a plurality of yarns, respectively.

This switch has an insulating housing 2 including a removable front cover 4 secured to the housing by snap-in structures between the housing and cover. This snap-in structure may include grooves at the top and bottom of the housing opening and complementary ribs at the top and bottom of the cover. The upper rib may first be inserted in its groove and the cover then pressed at the bottom to cause the lower rib to snap into its groove, the housing and cover being made of nylon or the like insulating material having enough resilience to afford such snap-in assembly of the cover.

A mounting bracket 6 is secured to the housing for snap-in mounting of the switch to a horizontally running strip or bar, this mounting bracket or clip also serving as one terminal, negative or ground, of the electrical circuit therein as shown in FIG. 6.

This electrical circuit extends from its negative terminal or ground at mounting bracket 6 through a fastener post 8 and a bracket plate 10 to crank shaft 12 which is the movable contact of the switch. This circuit then continues from contact plate 14 which is the resilient stationary contact of the switch through lamp bulb l6 and resistor 18 in parallel to its positive terminal at lamp terminal plate 20 as shown in FIGS. 2 and 6.

Housing 2 comprises a molded shallow box having upper and lower, left and right and rear walls and being open at the front for closure by cover 4. The left wall is provided with an integrally molded mounting hook 2a shown in FIGS. 2 and 3 over which rectangular aperture 6a of the mounting bracket is hooked whereafter fastener post 8 is inserted through aligned holes in mounting bracket 6 and the left wall of the housing. To secure post 8 in place, it is provided at its inner end with an annular groove and bracket plate 10 is provided with a pair of parallel, coplanar, rearwardlyextending fingers that enter opposite sides of this groove to grip the inner end of the post and secure it in place and electrically connect mounting bracket 6 to bracket plate 10. These fingers are rightwardly bowed to pull the head of fastener post 8 tightly against the mounting bracket to provide mechanically tight and electrically pressure connections at both ends of the fastener post.

Housing 2 is also provided with stationary thread guiding means. This means comprises integrally molded upper and lower, parallel eyelet supports 2b and 2c extending laterally from the right wall of the housing and connected at their ends by an integral, vertical bar 2d for ridigity. As shown in FIG. 1, the upper eyelet support is provided with means for snap-in mounting of a ceramic eyelet. This means comprises a hole 2e surrounded by inwardly directed short resilient fingers 2f that flex and snap into annular groove 22a of eyelet 22 when the eyelet is pressed thereinto from above. Lower eyelet support 2c is provided with similar means for snap-in mounting of ceramic eyelet 24. While the two eyelets are similar, upper eyelet 22 is snapped down from above while lower eyelet 24 is snapped up from below. Since each eyelet 22 and 24 has a larger flange on one side of its annular groove than on the other side, the larger flange of eyelet 22, being above, serves to hold down the divided end 26a of thread tension guide bracket 26 whereas the larger flange of eyelet 24, being below, affords gripping for removal of this eyelet.

The parts within the housing comprise the aforementioned bracket plate 10 having its main portion flat against the rear wall of the housing and its left end 10a being bent forwardly. This left end is provided with a cutout 10b leaving two rearwardly-extending bowed fingers, as aforementioned, for gripping post 8 and biasing it toward the right. The upper or right-hand portion of bracket plate is provided with an inclined slot 10c, most clearly shown in FIGS. 2 and 6, forming a pivot support for one side of crank shaft 12. The lower right-end tip of bracket plate 10 is bent forwardly to provide a stop 10d for overcenter spring tension adjusting screw 28. In addition, the bracket plate is provided with a small round hole that fits over an integrally molded stud 2g on the rear wall of the housing to rigidly secure the bracket plate in its place. This stud 2g also is located to serve as a stop for crank shaft 12 to facilitate assembly of the trip lever thereon.

Front cover 4 is provided with a small hole 4a shown in FIG. 4 forming a pivot support for the other side of crank shaft 12. This hole has a round center and lateral wings providing access for the flattened end of the crank shaft and providing a rounded bearing surface for the crank shaft against which it is biased by overcenter spring 30 as hereinafter described. The inner surface of the cover around this hole is provided with an integrally molded pad 4b of extra thickness to provide a bearing surface for the crank shaft.

The crank shaft is provided with means for retaining one end hook of overcenter spring 30. This means comprises a shallow V-bend 12a in its swingable center portion as shown in FIG. 4.

The crank shaft is further provided with flattened portions 12b and 120 at its external ends as shown in FIGS. 1 and 4 for retaining thread tension detecting arm or trip lever 32 as hereinafter described.

Adjusting screw 28 is provided with means for retaining the other end hook of overcenter spring 30. This means comprises an integrally-molded forward stud 28a shown in FIG. 2 that extends from the head of this screw to the front cover as shown in FIG. 4.

The threaded shaft 28b of the adjusting screw extends into a tapped hole in a fixed but rotatable adjusting nut 34 that extends out through a hole in the lower wall of the housing to be accessible for manual adjustment of the overcenter spring tension. To keep this nut from riding up on the screw, it is provided with a flange 34a rotatably confined between the lower wall of the housing and lamp terminal plate that is fixed in the housing as hereinafter described and having a slot through which the screw freely extends.

The aforementioned contact plate 14 is shown in FIGS. 2 and 5. As shown in FIG. 2 in dotted lines, its upper end 14a is resiliently deflectable when engaged by the crank shaft to close the contact. This contact plate is provided with a rear tab 14b as shown in FIG. 5 having a gripper type aperture 140 that fits over a lug 2h on the rear wall of the housing to retain the contact plate in place. This contact plate is also provided with a pair of forwardly-extending fingers 14d between which one wire of resistor 18 is forced to make an electrical connection. This contact plate is further provided with a leftwardly and then forwardly extending connector tab l4e, positioned beneath an abutting wall2j within the housing compartment against which the upper surface of the connector tab stops when the lamp bulb is screwed against the lower surface thereof to housing in a horizontal plane to provide space for free turning of the flange of adjusting nut 34. For this purpose, the right-hand end of portion 20b is held in a groove in the right wall of the housing and the left-hand end thereof including the perforated connector tab 20c is held in a notch in the left wall of the housing while the center thereof is spaced from the lower wall of the housing by an integrally molded rib 2k. As aforementioned, this portion 20b is provided with a rearwardly opening slot providing clearance for threaded shaft 28b of the adjusting screw. This portion 20b is also provided with a hole having its edge formed into a oneturn thread forming a lamp socket. Connector tab 20c is formed into a vertical plane as shown in FIG. 2 and extends outside through the notch in the housing wall for connection to an external circuit.

Tension arm or trip lever 32 is a generally U-shaped wire having its two ends flattened, slotted and swaged into curved form, the narrow slots snugly receiving the respective flattened ends of the crank shaft when the two arms of the trip lever are spread apart and allowed to spring on the crank. This assembly holds the trip lever rigidly to the crank shaft so that the trip lever will rotate the crank shaft to close the contacts when the thread or yarn breaks. The two arms of the trip lever also have corresponding bends therein at about their midportions so that the lower portion of the trip lever is vertical in operative position as shown in FIG. 2. The lower portion of the trip lever is bent at a right angle toward the right and the yoke portion 32a thereof is provided with a reentrant bend forming a near circle for retaining a ceramic eyelet 36, this eyelet being in vertical alignment with eyelets 22 and 24 in operative position of the trip lever and in parallel horizontal planes.

Thread tension guide bracket 26 is readily removable and affords snap-in mounting as shown in FIG. 1. For this purpose, its right end 26a is divided to fit under the upper flange of eyelet 22. Its left end portion is provided with a pair of legs 26b having inwardly curved tips 260 as shown in FIG. 1 that snap into respective slots 6b formed in mounting bracket 6. From the top of these legs the thread tension guide bracket inclines down toward the divided end 26a as shown in FIG. 2. This bracket 26 is formed from a generally flat strip of metal and a tongue 26d is sheared from its aforesaid inclined portion and is bent up perpendicular thereto to retain a plurality of perforated, dished, flat-bottom tension washers 38 freely thereon between which the thread passes. As shown in FIG. 2, the first washer is placed on tongue 26d upside down and one or more washers are placed on top of it upside up so that the thread runs between the bottoms of the first and second washers to provide friction for imparting tension on the thread beyond this point. The bottoms of the washers have an annular flat section so that the difference between the hole diameter and the tongue width does not negate the washers providing a constant friction pressure. Were this annular section rounded rather than flat, it would create a gap due to the upper washer displacing in the direction of yarn passage. The left tail end 26e of this bracket is bent up substantially perpendicular to the thread path between the washers and its extreme end is then bent to the right to extend substantially horizontally over the upper end of tongue 26d to retain the washers on the tongue. This perpendicular tail end portion is provided with a cutout leaving a pair of arcuate sides for embracing and retaining a ceramic eyelet 40 in snap-in and snap-out fashion in line with and for guiding the thread for entry between the wash ers.

As shown in FIGS. l-3, mounting bracket 6 has an upper hook 6c and a lower catch 6d and a pair of side panels 6e. This upper hook is formed by an upper tab bent toward the left with its tip bent down. The lower catch is formed by a lower tab bent toward the left with its end portion bent first up and then inclined down. The side panels are formed by tabs bent toward the left from the front and rear sides of the bracket. Notches formed in the upper edges of these side panels along with the adjacent edges of upper hook 6c form slots 61; into which the legs of thread tension guide bracket 26 are snapped.

The housing is provided with two pairs of stops for the trip lever, a first or lower pair of stops 2m for stopping it in its lowered or operative position and a second or upper pair of stops 2n for stopping it in its upper or tripped position as shown in solid and broken lines, respectively, in FIG. 2.

The yarn detector switch is further provided with a trapper 42 formed from round music wire or the like. This trapper holds the thread under normal slackening when knitting certain patterns to prevent unwanted tripping of the switch. This wire is formed into a generally V-shape at its midportion as shown in FIG. 1 with the end portions 42a of the arms thereof bent parallel to one another and their tips bent at right angles toward one another. This enables the arms of the trapper to be spread apart and released to allow the coaxial tips to enter holes and horizontal slots adjacent thereto in the front and rear of the housing for mounting the same. The apex 42b of the V-shape is elongated with the bent back yoke portions of the wire being in closely-spaced relation forming a cleft to frictionally hold the thread therein if it should be pulled thereinto upon partial swinging of the trip lever.

The thread normally runs through the yarn detecto switch as shown in solid lines if FIG. 2. Thus, the thread enters through eyelet 40 and then passes between washers 38 and down through aligned eyelets 22, 24 and 36. The tension in the thread holes trip lever 32 down in the position shown in FIG. 2. If the thread should break or end to release eyelet 36, overcenter spring 30 rotates crank shaft 12 counter-clockwise swinging the trip lever to the broken line position shown in FIG. 2 and closing the contact. The contact is closed by the swingable portion 12a of the crank shaft engaging upper end 14a of the contact plate. This closes the circuit from ground at mounting bracket 6 to terminal plate 20 to stop the knitting machine and to light lamp 16 as an indication thereof.

When knitting certain patterns, if a lesser amount of slack occurs in the thread leaving eyelet 36, trip lever 32 pivots counter-clockwise partially and draws the thread into the cleft in trapper 42. Thus, the trapper prevents the spring-biased trip lever from pulling more thread through eyelet 24 and the trip lever is held short of contact closure. When the slack is taken up again by the knitting machine, the trip lever is pulled down again to the position shown in FIG. 2.

While the apparatus hereinbefore described is effectively adapted to fulfill the objects stated, it is to be understood that the invention is not intended to be confined to the particular preferred embodiment of lower yarn detector switch disclosed, inasmuch as it is susceptible of various, modifications without departing from the scope of the appended claims.

I claim:

1. A yarn detector device for a knitting machine comprising:

an insulating housing;

a pair of electrical terminals on said housing;

a toggle spring mechanism comprising an overcenter spring biased crank shaft in said housing with the opposite ends of said crank shaft extending out through opposite walls of said housing;

an electric circuit within said housing extending between said terminals;

contacts within said housing responsive to operation of said crank shaft for closing said electric circuit;

and external thread passage means through which the thread passes before entering the knitting machine comprising:

thread guiding means and means mounting the same on said housing; a trip lever for detecting a break or end of thread to operate said crank shaft to close said contacts;

and quick disconnect joint means between said trip lever and said crank shaft enabling ready replacement thereof.

2. The invention defined in claim 1, wherein:

said trip lever comprises a generally U-shaped trip lever having said quick disconnect joint means between its two arms and the opposite ends of said crank shaft;

said thread guiding means comprises an eyelet through which the thread passes;

and a snap-in mounting between said eyelet and the yoke portion of said U-shaped trip lever.

3. The invention defined in claim 1, wherein said thread guiding means comprises:

an eyelet;

and said means mounting the same on said housing comprises a snap-in mounting between said eyelet and said housing providing a stationary thread guide.

4. The invention defined in claim 1, wherein said thread guiding means comprises:

a quick disconnect thread guiding and tensioning mechanism mounted on said housing affording ready removal thereof and having:

a quick disconnect bracket and means mounting the same on said housing;

a snap-in eyelet mounted on said bracket for guiding the thread;

and tensioning washers mounted on said bracket between which the thread passes.

5. The invention defined in claim 4 wherein said quick disconnect bracket and means mounting the same on said housing comprises:

a mounting bracket for said housing having a pair of slots therein;

legs on said quick disconnect bracket engaging said slots to removably secure one end thereof;

and a snap-in eyelet mounted to said housing for securing the other end of said quick disconnect bracket and serving as a stationary thread guiding means through which the thread passes to said trip lever.

6. The invention defined in claim 1, wherein said said trapper comprises a pair of arms that may be yarn detec or devi ompri e spread apart and allowed to spring toward one ana trapper for holding the thread in case of normal h Slack thFreinwhen knitting Certain P F to P and said housing comprises a pair of slots for receiv- Vent Sald mp lever from closmg 581d contacts ing the ends of said arms of said trapper for quick thereby to prevent machine shutdown. 7. The invention defined in claim 6, wherein said trapper comprises:

a generally V-shaped member mounted on said housdisconnect mounting thereof. 9. The invention defined in claim 1, wherein said electric circuit comprises:

ing and having a thread gripping cleft at its apex to 10 a I grip the thread and prevent the trip lever from pulland an mdlcator lamp extendmg through a wall of ing more thread th r by t prevent th i [ever said housing and connected across said resistor for from tripping. indicating a tripped condition. 8. The invention defined in claim 7, wherein: 

1. A yarn detector device for a knitting machine comprising: an insulating housing; a pair of electrical terminals on said housing; a toggle spring mechanism comprising an overcenter spring biased crank shaft in said housing with the opposite ends of said crank shaft extending out through opposite walls of said housing; an electric circuit within said housing extending between said terminals; contacts within said housing responsive to operation of said crank shaft for closing said electric circuit; and external thread passage means through which the thread passes before entering the knitting machine comprising: thread guiding means and means mounting the same on said housing; a trip lever for detecting a break or end of thread to operate said crank shaft to close said contacts; and quick disconnect joint means between said trip lever and said crank shaft enabling ready replacement thereof.
 2. The invention defined in claim 1, wherein: said trip lever comprises a generally U-shaped trip lever having said quick disconnect joint means between its two arms and the opposite ends of said crank shaft; said thread guiding means comprises an eyelet through which the thread passes; and a snap-in mounting between said eyelet and the yoke portion of said U-shaped trip lever.
 3. The invention defined in claim 1, wherein said thread guiding means comprises: an eyelet; and said means mounting the same on said housing comprises a snap-in mounting between said eyelet and said housing providing a stationary thread guide.
 4. The invention defined in claim 1, wherein said thread guiding means comprises: a quick disconnect thread guiding and tensioning mechanism mounted on said housing affording ready removal thereof and having: a quick disconnect bracket and means mounting the same on said housing; a snap-in eyelet mounted on said bracket for guiding the thread; and tensioning washers mounted on said bracket between which the thread passes.
 5. The invention defined in claim 4 wherein said quick disconnect bracket and means mounting the same on said housing comprises: a mounting bracket for said housing having a pair of slots therein; legs on said quick disconnect bracket engaging said slots to removably secure one end thereof; and a snap-in eyelet mounted to said housing for securing the other end of said quick disconnect bracket and serving as a stationary thread guiding means through which the thread passes to said trip lever.
 6. The invention defined in claim 1, wherein said yarn detector device comprises: a trapper for holding the thread in case of normal slack therein when knitting certain patterns to prevent said trip lever from closing said contacts thereby to prevent machine shutdown.
 7. The invention defined in claim 6, wherein said trapper comprises: a generally V-shaped member mounted on said housing and having a thread gripping cleft at its apex to grip the thread and prevent the trip lever from pulling more thread thereby to prevent the trip lever from tripping.
 8. The invention defined in claim 7, wherein: said trapper comprises a pair of arms that may be spread apart and allowed to spring toward one another; and said housing comprises a pair of slots for receiving the ends of said arms of said trapper for quick disconnect mounting thereof.
 9. The invention defined in claim 1, wherein said electric circuit comprises: a resistor; and an indicator lamp extending through a wall of said housing and connected across said resistor for indicating a tripped condition. 